Aging of hemp shiv used for concrete

Abstract Functional properties of vegetal concretes, such as hygrothermal and acoustical properties, are brought by the microstructure of the vegetal particles. However, data are necessary to develop biobased insulation materials by providing results on their long-term behaviour, and only few studies focus on this topic. A first step is to characterise the behaviour of vegetal aggregates in bulk. In this study, hemp shiv is stored for two years in three different conditions: a static environment used as reference, accelerated aging conditions based on humidification and drying cycles, and an exterior aging. The potential evolution of functional properties of particles is monitored with time and depending on the aging conditions. These evolutions are understood thanks to a study at a microscopic scale, where the microstructure of the particles is investigated. This study shows that no variation is observed for the reference conditions, whereas four phenomena linked to aging can be identified for accelerated and exterior aging conditions: a mass loss, volume variations of the particles and an opening of the aggregates porosity for both storing conditions. The last one, only observed for exterior aging, is a modification of the pore size distributions.